Dating - Ultra sound vs midwife

[Joannezipan]

I was a late booker - yeah didn't know I was pregnant - long story and this is my first baby. I had a dating scan at the hospital which said I was 24 weeks based on measurements they took. But the midwife thinks I'm about 3 weeks further along than that based on the measurements she took. So my question is why do you guys think, how accurate are the dating methods?

I was talking about this with my mum, what if the baby is bigger or smaller then the 'guideline measurements'. But I'm quite sure your hospital/Drs etc will go on the dates from your ultrasound. Do you know when your LMP was? If so try and see what date that gives you.

unfortunately not, PCOS gives me very irregular periods. Sometimes months go by with nothing so regular dating methods don't really work. :(

I would go off the ultrasound. It's hard to tell the exact dates after about 14 weeks because they all grow at varying rates after that but measuring the height of fundus (is that what your midwife did?) is less accurate than measuring the actual baby.

My ultrasound dated me 23rd August for DS but whenever the midwife was measuring my tummy I was always anywhere from 2-4 weeks ahead, for example at 32 weeks I was measuring 36. I had scans every four weeks because I had bleeding and after about 20 weeks he was always measuring slightly ahead but never by more than a week. He arrived on his due date and was on the big side. I asked the delivery midwife if that meant my dates were wrong and he was overdue and she told me he didn't have the look of an overdue baby (supposedly they have certain characteristics) and he was covered in plenty of vernix and still had some languno on his back - yeah, my baby had a hairy back.

Neither method is 100% but I'd go off ultrasound myself.

I would have thought the scan would be more acurate. Just because they are 'seeing' the baby?

Scans always date me as further along than I actually am. (I have big babies) But I knew my dates. As you don't, I would go with the scan. The only concern I would have is going past that date and having to opt for a (possibly unnecessary) induction.

It is all a bit confusing, I guess it is wait and see time for the next scan. I'm just having nightmares about going into labour in the office!

The scan will be more accurate than the MW - but neither will be particularly accurate at this stage of the pregnancy.

At your next appointment, I'd ask for a range in addition to an absolute EDD. Then consider whether you're expecting a large or small baby based your (and your DH's) family history.

As its you're first baby you're less likely to go into labour early, and you're less likely to have a fast labour - the very early stages of labour can go on quite a while (I had a 5 day latent phase, although active labour was then only 7 hours) so you should have plenty of time to get yourself to a better place than the office toilet :o